Paolo Messina - Academia.edu (original) (raw)
Papers by Paolo Messina
—Deep Convolutional Neural Networks (DCNNs) have recently been applied successfully to a variety ... more —Deep Convolutional Neural Networks (DCNNs) have recently been applied successfully to a variety of vision and multimedia tasks, thus driving development of novel solutions in several application domains. Document analysis is a particularly promising area for DCNNs: indeed, the number of available digital documents has reached unprecedented levels, and humans are no longer able to discover and retrieve all the information contained in these documents without the help of automation. Under this scenario, DCNNs offers a viable solution to automate the information extraction process from digital documents. Within the realm of information extraction from documents, detection of tables and charts is particularly needed as they contain a visual summary of the most valuable information contained in a document. For a complete automation of visual information extraction process from tables and charts, it is necessary to develop techniques that localize them and identify precisely their boundaries. In this paper we aim at solving the table/chart detection task through an approach that combines deep convolutional neural networks, graphical models and saliency concepts. In particular, we propose a saliency-based fully-convolutional neural network performing multi-scale reasoning on visual cues followed by a fully-connected conditional random field (CRF) for localizing tables and charts in digital/digitized documents. Performance analysis carried out on an extended version of ICDAR 2013 (with annotated charts as well as tables) shows that our approach yields promising results, outperforming existing models.
Langmuir, 2009
The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been sub... more The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been substantially improved by the work presented by Komeda and Manassen (Komeda, T.; Manassen, Y. Appl. Phys. Lett. 2008, 92, 212506). The application of this technique to molecular paramagnets requires the positioning and anchoring of paramagnetic molecules at surfaces. It also requires the possibility of tunneling high current densities into the STM-molecule-substrate tunneling junction. In this letter, we exploit the self-assembly of 1,10-phenantroline on the Au(111) surface to form a diamagnetic matrix that hosts individual molecules and dimers of diphenyl-2-picryl-hydrazyl (DPPH). STM measurements are used to characterize the molecular layer. Electron spin resonance (ESR) measurements elucidate the role of thermal annealing in the preservation of the paramagnetic nature of the DPPH molecules.
Nanotechnology, 2009
We report here on the design, construction and testing of a vacuum compatible AC-DC amplification... more We report here on the design, construction and testing of a vacuum compatible AC-DC amplification system for low signal measurements with scanning probes. The most important feature of this new amplification system is incorporated within the head of a scanning tunneling microscope (STM). This is achieved with a very low thermal dissipation radio frequency amplifier at the STM head. The amplifier gain is higher than 40 dB and has a 50 dB maximum. Further, the AC noise figure is 0.7 dB between 100 and 1000 MHz. The noise induced in the DC amplifier is less than 2 pA RMS (root mean square), which enables the microscope to scan over soft insulating molecular layers. Thermal drift at the STM tip-sample interface is below 0.1 nm min(-1) both in air and in vacuum operation. Atomic resolution on highly oriented pyrolytic graphite surfaces is reliably achieved. Spin noise measurements are provided as an example of an application.
Inorganica Chimica Acta, 2007
We present our recent efforts in the build-up of a room temperature electron spin noise scanning ... more We present our recent efforts in the build-up of a room temperature electron spin noise scanning tunnelling microscope (ESN-STM) designed for ultra-thin molecular films investigation. We describe here the first results obtained with this system on a commercial paramagnetic molecule deposited on Au(1 1 1) surfaces, namely 1,1-diphenyl-2-picrylhydrazyl (DPPH). Further we briefly present our ongoing work on the preparation and characterization of a new class of samples for this instrumentation. These are based on the self-assembling on surfaces of functionalized organic radicals. We suggest here a complete procedure to assess a good candidate molecule for ESN-STM experiments through X-band CW-ESR, standard STM investigations and ToF-SIMS analysis.
Journal of Applied Physics, 2007
The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. ... more The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. An ensemble of spins can produce a coherent signal at the frequency of a static magnetic field, known as spin noise, an effect due to the statistical polarization of small ensembles. The difficulty of these measurements is that the signal is extremely small -even if electron spins are detected. Although the statistical polarization of N spins dominates the Boltzmann statistics if N approaches unity, a more sensitive tool is requested to measure the polarization of the magnetic moment of a single spin. In this paper we report on the verification of recent results on the detection of spin noise from paramagnetic molecules of BDPA (α,γ-Bisdiphenylene-β-phenylallyl) by Durkan and coworkers.[C. Durkan and M. E. Welland, Appl. Phys. Lett. 80, 458 (2002)] We also present new results on a second paramagnetic specie, DPPH (1,1-Diphenyl-2-picrylhydrazyl), deposited on Au(111) surfaces. ESR spectra from ultrathin films of DPPH and BDPA grown on Au(111) are
ESR-STM is a technique able to detect noise at the Larmor frequency in the tunnelling current ass... more ESR-STM is a technique able to detect noise at the Larmor frequency in the tunnelling current associated with the spin dynamics of a single paramagnetic center on the surface. Several questions concerning details of this phenomenon in different magnetic fields and tunnelling currents, and for different paramagnetic centers are still debated. In this paper we describe the construction and the testing of an instrument able to detect the ESR-STM signal from organic paramagnetic molecules (DPPH and BDPA) deposed on Au(111) at different magnetic fields. First results on these molecules are presented.
Few examples of the exploitation of molecular magnetic properties in molecular electronics are kn... more Few examples of the exploitation of molecular magnetic properties in molecular electronics are known to date. Here, we propose the realization of self assembled monolayers (SAM) of a particular stable organic radical. This radical is meant to be used as a standard molecule on which to prove the validity of a single spin reading procedure known as ESR-STM. We demonstrate here that the radical is chemically anchored at the surface, preserves its magnetic functionality and can be imaged by STM. STM and ESR investigations of the molecular film are reported. We also discuss a range of possible applications, further than ESR-STM, of magnetic monolayers of simple purely organic magnetic molecules.
The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. ... more The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. An ensemble of spins can produce a coherent signal at the frequency of a static magnetic field, known as spin noise, an effect due to the statistical polarization of small ensembles. The difficulty of these measurements is that the signal is extremely small, even if electron spins are detected. Although the statistical polarization of N spins dominates the Boltzmann statistics if N approaches unity, a more sensitive tool is requested to measure the polarization of the magnetic moment of a single spin. In this paper we report on the verification of recent results on the detection of spin noise from paramagnetic molecules of BDPA alpha,gamma,Bisdiphenylene,betha,phenylallyl by Durkan and coworkers. C. Durkan and M. E. Welland, Appl. Phys. Lett. 80, 458 2002 We also present new results on a second paramagnetic specie, DPPH (1,1,Diphenyl,2.picrylhydrazyl), deposited on Au(111) surfaces. ESR spectra from ultrathin films of DPPH and BDPA grown on Au(111) are reported. We prove that the paramagnetic molecules preserve their magnetism on the surface. These data and a thorough analysis of the signal recovery apparatus help to understand the low statistical recurrence of the spin noise in the data set . A thorough description of the experimental apparatus together with an analysis of the parameters that determine the sensitivity are also presented.
Reading and manipulating the spin status of single magnetic molecules is of paramount importance ... more Reading and manipulating the spin status of single magnetic molecules is of paramount importance both for applicative and fundamental purposes. The possibility to combine electron spin resonance (ESR) and scanning tunnelling microscopy (STM) has been explored one decade ago. A few experiments have raised the question whether or not an EPR spectrum of single molecule is detachable. Only a few data have been reported in modern surface science literature. To date it has yet to be proven till which extent ESR can be reliably and reproducibly performed on single molecules. We are setting up a new ESR-STM "spectrometer" to verify and study the effect of spin-spin correlations in the frequency spectrum of the tunneling current which flows through a single magnetic adsorbate and a metal surface. Here, we discuss, the major experimental challenges that we are attempting to overcome.
Journal of The American Chemical Society, 2002
Chirality is a topic extensively studied in chemistry, biology, and pharmacology. It is encounter... more Chirality is a topic extensively studied in chemistry, biology, and pharmacology. It is encountered at different levels, from single molecules and supramolecular assemblies to living organisms. Besides organic molecules, coordination compounds offer a rich variety of chiral species attracting strong current interest. 5,6 Recent studies revealed that by scanning tunneling microscopy (STM), detailed insight into chirality phenomena at surfaces can be gained, including chiral recognition and chirality determination of single molecules, supramolecular assemblies, and extended enantiomerically pure overlayers. 7-15 Many of these studies have shown that surfaces can be used as a symmetry breaking agent to induce enantiomeric separation or enantiomorphic ordering in supramolecular assemblies produced by deposition of a racemate, prochiral, or even achiral molecules. Here we report single-molecule level STM observations of chiral complexes generated by the assembly of achiral components and metal centers at a metal surface. Following co-deposition of iron atoms and 1,3,5-tricarboxylic benzoic acid (trimesic acid, TMA) on Cu(100), we have found that the molecules react with the metal centers to chiral complexes stabilized by metal-ligand interactions. To our knowledge, this represents the first direct observation of a chiral coordination compound on surfaces.
Journal of The American Chemical Society, 2003
We demonstrate the rational design of nanoporous two-dimensional supramolecular structures by the... more We demonstrate the rational design of nanoporous two-dimensional supramolecular structures by the hierarchical assembly of organic molecules and transition metal atoms at surfaces. Single-molecule level observations with scanning tunneling microscopy monitor the successive aufbau of structures with increasing complexity. From the primary components secondary mononuclear chiral complexes are formed, which represent antecedents for tertiary polynuclear metal-organic nanogrids. These nanogrids represent the constituents of the eventually evolving two-dimensional networks comprising homochiral nanocavity arrays. Our findings visualize the evolution of complex matter in an exemplary way: from per se achiral species via chiral intermediates to mesoscale dissymmetric structures.
We report the construction of complex metal-organic assemblies at surfaces using concepts from co... more We report the construction of complex metal-organic assemblies at surfaces using concepts from coordination chemistry. Well-ordered supramolecular assemblies and metal-organic coordination networks with specific topologies and a high structural stability have been fabricated under ultra-high vacuum conditions by sequential deposition of polyfunctional organic molecules and Fe atoms onto an atomically clean Cu(100) substrate. The structures were investigated at the molecular level by in-situ scanning tunneling microscopy. The precise control of the concentration ratio of the components and the annealing treatment allow for the assembly of distinct architectures.
—Deep Convolutional Neural Networks (DCNNs) have recently been applied successfully to a variety ... more —Deep Convolutional Neural Networks (DCNNs) have recently been applied successfully to a variety of vision and multimedia tasks, thus driving development of novel solutions in several application domains. Document analysis is a particularly promising area for DCNNs: indeed, the number of available digital documents has reached unprecedented levels, and humans are no longer able to discover and retrieve all the information contained in these documents without the help of automation. Under this scenario, DCNNs offers a viable solution to automate the information extraction process from digital documents. Within the realm of information extraction from documents, detection of tables and charts is particularly needed as they contain a visual summary of the most valuable information contained in a document. For a complete automation of visual information extraction process from tables and charts, it is necessary to develop techniques that localize them and identify precisely their boundaries. In this paper we aim at solving the table/chart detection task through an approach that combines deep convolutional neural networks, graphical models and saliency concepts. In particular, we propose a saliency-based fully-convolutional neural network performing multi-scale reasoning on visual cues followed by a fully-connected conditional random field (CRF) for localizing tables and charts in digital/digitized documents. Performance analysis carried out on an extended version of ICDAR 2013 (with annotated charts as well as tables) shows that our approach yields promising results, outperforming existing models.
Langmuir, 2009
The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been sub... more The detection of spin noise by means of scanning tunneling microscopy (STM) has recently been substantially improved by the work presented by Komeda and Manassen (Komeda, T.; Manassen, Y. Appl. Phys. Lett. 2008, 92, 212506). The application of this technique to molecular paramagnets requires the positioning and anchoring of paramagnetic molecules at surfaces. It also requires the possibility of tunneling high current densities into the STM-molecule-substrate tunneling junction. In this letter, we exploit the self-assembly of 1,10-phenantroline on the Au(111) surface to form a diamagnetic matrix that hosts individual molecules and dimers of diphenyl-2-picryl-hydrazyl (DPPH). STM measurements are used to characterize the molecular layer. Electron spin resonance (ESR) measurements elucidate the role of thermal annealing in the preservation of the paramagnetic nature of the DPPH molecules.
Nanotechnology, 2009
We report here on the design, construction and testing of a vacuum compatible AC-DC amplification... more We report here on the design, construction and testing of a vacuum compatible AC-DC amplification system for low signal measurements with scanning probes. The most important feature of this new amplification system is incorporated within the head of a scanning tunneling microscope (STM). This is achieved with a very low thermal dissipation radio frequency amplifier at the STM head. The amplifier gain is higher than 40 dB and has a 50 dB maximum. Further, the AC noise figure is 0.7 dB between 100 and 1000 MHz. The noise induced in the DC amplifier is less than 2 pA RMS (root mean square), which enables the microscope to scan over soft insulating molecular layers. Thermal drift at the STM tip-sample interface is below 0.1 nm min(-1) both in air and in vacuum operation. Atomic resolution on highly oriented pyrolytic graphite surfaces is reliably achieved. Spin noise measurements are provided as an example of an application.
Inorganica Chimica Acta, 2007
We present our recent efforts in the build-up of a room temperature electron spin noise scanning ... more We present our recent efforts in the build-up of a room temperature electron spin noise scanning tunnelling microscope (ESN-STM) designed for ultra-thin molecular films investigation. We describe here the first results obtained with this system on a commercial paramagnetic molecule deposited on Au(1 1 1) surfaces, namely 1,1-diphenyl-2-picrylhydrazyl (DPPH). Further we briefly present our ongoing work on the preparation and characterization of a new class of samples for this instrumentation. These are based on the self-assembling on surfaces of functionalized organic radicals. We suggest here a complete procedure to assess a good candidate molecule for ESN-STM experiments through X-band CW-ESR, standard STM investigations and ToF-SIMS analysis.
Journal of Applied Physics, 2007
The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. ... more The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. An ensemble of spins can produce a coherent signal at the frequency of a static magnetic field, known as spin noise, an effect due to the statistical polarization of small ensembles. The difficulty of these measurements is that the signal is extremely small -even if electron spins are detected. Although the statistical polarization of N spins dominates the Boltzmann statistics if N approaches unity, a more sensitive tool is requested to measure the polarization of the magnetic moment of a single spin. In this paper we report on the verification of recent results on the detection of spin noise from paramagnetic molecules of BDPA (α,γ-Bisdiphenylene-β-phenylallyl) by Durkan and coworkers.[C. Durkan and M. E. Welland, Appl. Phys. Lett. 80, 458 (2002)] We also present new results on a second paramagnetic specie, DPPH (1,1-Diphenyl-2-picrylhydrazyl), deposited on Au(111) surfaces. ESR spectra from ultrathin films of DPPH and BDPA grown on Au(111) are
ESR-STM is a technique able to detect noise at the Larmor frequency in the tunnelling current ass... more ESR-STM is a technique able to detect noise at the Larmor frequency in the tunnelling current associated with the spin dynamics of a single paramagnetic center on the surface. Several questions concerning details of this phenomenon in different magnetic fields and tunnelling currents, and for different paramagnetic centers are still debated. In this paper we describe the construction and the testing of an instrument able to detect the ESR-STM signal from organic paramagnetic molecules (DPPH and BDPA) deposed on Au(111) at different magnetic fields. First results on these molecules are presented.
Few examples of the exploitation of molecular magnetic properties in molecular electronics are kn... more Few examples of the exploitation of molecular magnetic properties in molecular electronics are known to date. Here, we propose the realization of self assembled monolayers (SAM) of a particular stable organic radical. This radical is meant to be used as a standard molecule on which to prove the validity of a single spin reading procedure known as ESR-STM. We demonstrate here that the radical is chemically anchored at the surface, preserves its magnetic functionality and can be imaged by STM. STM and ESR investigations of the molecular film are reported. We also discuss a range of possible applications, further than ESR-STM, of magnetic monolayers of simple purely organic magnetic molecules.
The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. ... more The measurement of spin noise in nuclei was pioneered on bulk samples more than two decades ago. An ensemble of spins can produce a coherent signal at the frequency of a static magnetic field, known as spin noise, an effect due to the statistical polarization of small ensembles. The difficulty of these measurements is that the signal is extremely small, even if electron spins are detected. Although the statistical polarization of N spins dominates the Boltzmann statistics if N approaches unity, a more sensitive tool is requested to measure the polarization of the magnetic moment of a single spin. In this paper we report on the verification of recent results on the detection of spin noise from paramagnetic molecules of BDPA alpha,gamma,Bisdiphenylene,betha,phenylallyl by Durkan and coworkers. C. Durkan and M. E. Welland, Appl. Phys. Lett. 80, 458 2002 We also present new results on a second paramagnetic specie, DPPH (1,1,Diphenyl,2.picrylhydrazyl), deposited on Au(111) surfaces. ESR spectra from ultrathin films of DPPH and BDPA grown on Au(111) are reported. We prove that the paramagnetic molecules preserve their magnetism on the surface. These data and a thorough analysis of the signal recovery apparatus help to understand the low statistical recurrence of the spin noise in the data set . A thorough description of the experimental apparatus together with an analysis of the parameters that determine the sensitivity are also presented.
Reading and manipulating the spin status of single magnetic molecules is of paramount importance ... more Reading and manipulating the spin status of single magnetic molecules is of paramount importance both for applicative and fundamental purposes. The possibility to combine electron spin resonance (ESR) and scanning tunnelling microscopy (STM) has been explored one decade ago. A few experiments have raised the question whether or not an EPR spectrum of single molecule is detachable. Only a few data have been reported in modern surface science literature. To date it has yet to be proven till which extent ESR can be reliably and reproducibly performed on single molecules. We are setting up a new ESR-STM "spectrometer" to verify and study the effect of spin-spin correlations in the frequency spectrum of the tunneling current which flows through a single magnetic adsorbate and a metal surface. Here, we discuss, the major experimental challenges that we are attempting to overcome.
Journal of The American Chemical Society, 2002
Chirality is a topic extensively studied in chemistry, biology, and pharmacology. It is encounter... more Chirality is a topic extensively studied in chemistry, biology, and pharmacology. It is encountered at different levels, from single molecules and supramolecular assemblies to living organisms. Besides organic molecules, coordination compounds offer a rich variety of chiral species attracting strong current interest. 5,6 Recent studies revealed that by scanning tunneling microscopy (STM), detailed insight into chirality phenomena at surfaces can be gained, including chiral recognition and chirality determination of single molecules, supramolecular assemblies, and extended enantiomerically pure overlayers. 7-15 Many of these studies have shown that surfaces can be used as a symmetry breaking agent to induce enantiomeric separation or enantiomorphic ordering in supramolecular assemblies produced by deposition of a racemate, prochiral, or even achiral molecules. Here we report single-molecule level STM observations of chiral complexes generated by the assembly of achiral components and metal centers at a metal surface. Following co-deposition of iron atoms and 1,3,5-tricarboxylic benzoic acid (trimesic acid, TMA) on Cu(100), we have found that the molecules react with the metal centers to chiral complexes stabilized by metal-ligand interactions. To our knowledge, this represents the first direct observation of a chiral coordination compound on surfaces.
Journal of The American Chemical Society, 2003
We demonstrate the rational design of nanoporous two-dimensional supramolecular structures by the... more We demonstrate the rational design of nanoporous two-dimensional supramolecular structures by the hierarchical assembly of organic molecules and transition metal atoms at surfaces. Single-molecule level observations with scanning tunneling microscopy monitor the successive aufbau of structures with increasing complexity. From the primary components secondary mononuclear chiral complexes are formed, which represent antecedents for tertiary polynuclear metal-organic nanogrids. These nanogrids represent the constituents of the eventually evolving two-dimensional networks comprising homochiral nanocavity arrays. Our findings visualize the evolution of complex matter in an exemplary way: from per se achiral species via chiral intermediates to mesoscale dissymmetric structures.
We report the construction of complex metal-organic assemblies at surfaces using concepts from co... more We report the construction of complex metal-organic assemblies at surfaces using concepts from coordination chemistry. Well-ordered supramolecular assemblies and metal-organic coordination networks with specific topologies and a high structural stability have been fabricated under ultra-high vacuum conditions by sequential deposition of polyfunctional organic molecules and Fe atoms onto an atomically clean Cu(100) substrate. The structures were investigated at the molecular level by in-situ scanning tunneling microscopy. The precise control of the concentration ratio of the components and the annealing treatment allow for the assembly of distinct architectures.